This Psalm is a maskil by "Eisan the Ezrachi." But who was Eisan (Eitan in Sephardi pronunciation)? Rashi says that, like Heiman, Eisan was one of the sons of Zerach (as per I Chronicles 2:6), but he notes a Talmudic tradition that Eisan is another name for the Patriarch Abraham (see Baba Basra 15a and Yalkut Shimoni on I Kings, remez 178). Whoever Eisan was, he was renowned for his brilliance. I Kings 5:11 says that G-d granted Solomon wisdom even greater than that of Eisan the Ezrachi!

Eisan says that he will sing of G-d's kindness forever. He will tell all generations of G-d's consistency in maintaining the world. Eisan says that the world is built on kindness, while the heavens run on consistency. ("Olam chesed yiboneh" - the world is built on kindness - is a familiar phrase. This is a sentiment that Abraham would rightly express, seeing as he epitomizes the trait of kindness. See also the statement of Shimon HaTzaddik in Avos 1:2, that kindness is one of the three things that causes the world to endure.)

Eisan continues that G-d has made a covenant with David, His chosen, to establish his descendants as the eternal dynasty. This causes rejoicing even among the heavenly spheres, who praise G-d's works, while the angels praise His consistency. There is no one even remotely like G-d, not even in the heavens. Even the mighty angels are awed by G-d. He created the universe and everything in it; His great power keeps it going. The angels around Him testify to this fact.

G-d rules the proud sea and calms its waves. He used the sea to conquer the powerful army of Egypt at the time of the Exodus. G-d rules over both Heaven and Earth, north and south. The majestic mountains sing G-d's praises. (The Radak says that seeing them causes US to praise G-d!) Only G-d has power in His metaphorical "hands." His equally-metaphorical "throne" is supported by righteousness and justice. Kindness and truth are always at His disposal.

Eisan praises the nation that hears the shofar being blown, for they walk in the light of G-d's "face." They rejoice constantly in G-d and are raised by His righteousness. He is the glory of their strength and they will prosper through His graces. (These verses are recited on Rosh Hashana after the shofar is blown.)

The king of Israel may be a shield to the nation, but he is only an instrument of G-d. G-d sent a message to the nation through His prophets that He aids the king in protecting them; for this, G-d has singled the king out. He caused David to be anointed and He empowers him. Enemies will not be able to take money by force and evil people will not be able to harm him. G-d will strike down David's opponents, leaving him with the kindness and consistency we mentioned earlier. G-d will grant David dominion over the islands of the sea and the nation of Aram, across the river from Israel. David will look to G-d as a Father and G-d will treat David like a first-born son. (Though he wasn't the first king of Israel, David was the first king of the permanent dynasty.) David will be foremost among the kings of the Earth and his dynasty will endure forever.

If David's descendants stray from the Torah and do not keep G-d's laws, then He will punish them appropriately, but He will not break His word to David. The House of David will never lose the monarchy as Saul did. Furthermore, G-d promises to David that his descendants will always be considered royalty, to the exclusion of all others. His dynasty will shine like the sun and be as reliable as the moon. (The moon waxes and wanes, but it always comes back. This is also true of the Davidic dynasty, which is why we say "David melech Yisroel chai v'kayam" - "David, king of Israel, lives and endures" - during Kiddush Levana, the monthly sanctification of the moon.)

Now that the Jews are in exile, there are those who question whether G-d has, in fact, kept these promises. After all, there's no more king! The nation is laid waste and enemies have gotten the upper hand. The throne of David fell and the dynasty was shamed. How long will G-d hide Himself from us? How long will He be angry with us for our sins? For what reason was man even created? It all seems so bleak! Death is inevitable and the Psalmist despairs of personally seeing the redemption. Where are the kindnesses that G-d promised David? May G-d recall the disgrace of the nation at enemy hands and send redemption through His Moshiach (the Messiah). Blessed is G-d forever - Amen and Amen! (The last part of the Psalm is so full of despair and negativity that one might misconstrue the author's intent and think that he is criticizing G-d, G-d forbid! This is clarified by the final verse that reiterates Eisan's praises of G-d.)

Psalm 89 is the last Psalm in the third "book."